1. Field of the Invention
The present invention relates to a lens module. More particularly, the present invention relates to a zoom lens module.
2. Description of Related Art
Referring to FIG. 1, in a conventional manual focusing lens module 10, a lens 110 is inserted into an internal ring 120, and the internal ring 120 is sustained between a focus-adjusting ring 130 and a spring 140. The focus-adjusting ring 130 has segmented steps, thus, when the focus-adjusting ring 130 is turned manually, the focus-adjusting ring 130 links the internal ring 120 and the lens 110 to move up and down along Y-axis to complete a focusing operation. However, the lens module 10 is not convenient to use because it focuses manually.
Referring to FIG. 2, in a conventional lens module 20 which focuses through a stepping motor, a lens 110 is inserted into an internal ring 120, and the internal ring 120 is sustained between a focus-adjusting ring 130′ and a spring 140. The focusing pattern of the lens module 20 is to control a stepping motor 150 electrically to drive a transmission mechanism, such as a screw rod, a turbine, a gear, or the focus-adjusting ring 130′, so as to move the internal ring 120 and the lens 110 up and down along axis Y to complete a focusing operation. Even though the lens module 20 focus automatically, the lens module 20 has large size and high manufacturing cost, and the power consumption thereof for focusing is high.
FIG. 3A and FIG. 3B are diagrams of two conventional lens modules which focus through voice coil motor. Referring to FIG. 3A first, in a lens module 30, a lens 110 is inserted into a magnetic permeable internal ring 160, and a magnet 170 is disposed at both sides of the magnetic permeable internal ring 160. Thus, the magnetic permeable internal ring 160 is prevented from moving about by the electromagnetic force produced between the magnet 170 and the magnetic permeable internal ring 160, so as to fix the position of the lens 110 on axis X. Besides, the focusing pattern of the lens module 30 is to produce different magnetic levitation forces by controlling the current passed through a coil 180, and accordingly to move the magnetic permeable internal ring 160 and the lens 110 up and down along axis Y. The focusing speed of the lens module 30 is slow, and after focusing, current has to be supplied to the coil 180 continuously to prevent the elasticity g of a spring 140 from moving the magnetic permeable internal ring 160 downwards and further to maintain the position of the lens 110. Thus, the lens module 30 consumes more electricity. In addition, to fix the position of the lens 110 on axis X with electromagnetic force, the problem of the lens 110 being tilted may be caused. Moreover, the performance of the lens module 30 in vibration test or falling test is not ideal.
Referring to FIG. 3B, in a conventional lens module 40, a lens 110 is inserted into a magnetic permeable internal ring 160′, and the magnetic permeable internal ring 160′ is prevented from moving about by a leading rod 185 to fix the position of the lens 110 on axis X. Besides, a sensor 190 is used for detecting the position of the magnetic permeable internal ring 160′ on axis Y and transmitting signal back to an application specific integrated circuit (ASIC) 195. The ASIC 195 drives the coil 180 according to the position of the magnetic permeable internal ring 160′ so as to move the magnetic permeable internal ring 160′ and the lens 110 to expected position and further to complete a focusing operation. It is noted that the manufacturing cost of the lens module 40 is high even though no current is continuously provided to the coil 180 after focusing.
Referring to FIG. 4, in a conventional two-stage electrical focusing lens module 50, a lens 110 is inserted into an internal ring 120′, and an annular magnet 196 is disposed outside of the internal ring 120′. The focusing pattern of the lens module 50 is as following: attraction or repellent force is produced between a coil 180 and the annular magnet 196 by changing the direction of the current provided to the coil 180 for driving the annular magnet 196, the internal ring 120′, and the lens 110 to move to the top end or the bottom end along axis Y. Besides, a magnetic permeable sheet metal 197 is magnetized partially, thus, while it is stopped to provide current to the coil 180 after focusing, if the lens 110 is moved to the top end, attraction force produces between the top magnetic permeable sheet metal 197 and the annular magnet 196 to fix the lens 110 at the top. Similarly, if the lens 110 is moved to the bottom, attraction force will be produced between the bottom magnetic permeable sheet metal 197 and the annular magnet 196 to fix the lens 110 at the bottom. However, the lens module 50 has only two-stage focusing function and the size thereof is large. Moreover, the manufacturing cost of the lens module 50 is increased by the high cost of the annular magnet 196.